Alkylation of hydrocarbons



Sptulfi, 1941. A. R. GOLDSBY ETI'AL 3 3 9 ALKYLATION OF- HYDR 0 CARBON S -F'iled June 18; 1938- INVENTORS ARTi-LIR R.GOLD5BY ERNEST F. PEVERE- BY LOUIS A. CLARKE 0535 a. ATCH A ORN YS Patented Sept. 16, 1941 ALKYLATIION or HYDROCARBONS Arthur R. Goldsby and Ernest F. Pevere, Beacon,

RBSSUED Louis A. Clarke, Fishkill, and George B. Hatch,

Beacon, N. Y., assignors to The Texas Company, New York, N. Y., a corporation of Delaware WM- 4 an Application June 18, 1938, Serial No. 214,488

4 Claims.

This invention relates to the alkylation of hydrocarbons and has to do with a process for the reaction of certain paraflin hydrocarbons with olefins to produce saturated hydrocarbons of high antiknock value, suitable for the manufacture of motor fuel.

More particularly the present invention is an improvement in the method for the alkylation of isoparaflins with olefins in the presence of sulfuric acid as the catalyst. The invention is particularly applicable to the alkylation of lower boiling iso'parafiins, such, as isobutane and isopentane, with normally gaseous olefins, including cracking still gases or a fraction thereof such as a fraction containing predominantly C4 hydrocarbons, or C3 hydrocarbons or a mixture of C3 and C4 hydrocarbons; propylene; iso'meric normal butenes; isobutylene, or polymers thereof, for example, diisobutylene and tri-isobutylene; or co-polymers resulting from the polymerization of one molecule of normal butene with one molecule of isobutylene.

In the alkylation of isoparaflins with olefins using sulfuric acid as a catalyst, it is customary to contact the mixture of olefin and isoparafiin with the acid under such conditions that alkylation of the isoparaffins with the olefin occurs to produce branch chain, saturated hydrocarbons. In a continuous typeof operation, wherein a stream of hydrocarbons is charged to the system and a stream of spent or partially spent sulfuric acid is withdrawn, there may be a substantial amount of olefins absorbed by the acid and lost or removed from the system with the withdrawn used acid. The loss of olefins in the used acid is particularly observed when the reaction is carried out in a preferred type of continuous multistage countercurrent operation, wherein the used acid immediately before withdrawal from the system is ordinarily contacted with the fresh hydrocarbon charge and tends to absorb olefins therefrom.

In accordance with the present invention, the used acid, before withdrawal from the alkylation system, is treated with the isoparafiin to strip the acid of its olefin content. Although'no restricting the invention to any particular theory of react-i on,

it is believed that the olefins absorbed by the acid alkylate the isoparafiin, which is in relatively high ratio to the olefins, during the stripping operation. As applied to a countercurrent flow type of operation, the stripping of the used acid may take place in one or more additional stages wherein only the isoparaflin, which may be the stream of isoparafiin charging stock, is contacted with the used acid.

As applied to a countercurrent type of operation using a multiple injection of the olefins between stages in a multi-stage operation, the olefins according to the invention may be injected into the hydrocarbon layer of the settlers, whereby the olefins are mixed with the reaction products containing a high proportion of isoparaffin to efiect dilution of the olefins before contacting the mixture with the acid catalystin a subsequent mixer.

The invention will be more fully understood from the following description read in connection with the accompanying drawing, which shows diagrammatically a sketch of one form of appa ratus for carrying out the process of the invention. In the drawing, thereis shown a five-stage countercurrent system, but the number of stages may vary, and it is to be understood that that a part of the invention, insofar as it relates broadly ing stock is introducedby the line I and pump 2 into a mixer 3 which is provided with a stirring mechanism 5. The charging stock may be mixed with additional isoparaflin, recycled in the system through the line 6, as explained more fully hereinafter. In the mixer 3, the isoparaffin is intimately'contacted with used acid, which may be spent or partially spent, vintroduced through the line 8. The acid may contain a substantial amount of absorbed olefins and it is intended that the acid be stripped of these olefins by contact with the isoparaflln in the mixer 3. Due to the high ratio of isoparafiin, favorable conditions are provided for the alkylation of the isoparaffin by the olefins. The acid and hydrocarbon mixture is transferred from the mixer 3 through the line 9 to a settler l0, wherein the stripped acid separates from the hydrocarbons and collects in the lower portion of the settler and may be with- Y drawn through the valve controlled line H. The mixer 3 and settler l0 comprise the acid stripping stage, wherein only isoparafiins are contacted with the used acid. While only one stage of acid stripping is shown, it is to be understood that any number may be used.

The hydrocarbons collect in the upper portion of the settler l0 and into this hydrocarbon layer is introduced a portion of the olefin charge by line M which communicates with the olefin charging line l5 containing a pump "5. By suitable adjustment of the valve l8 in the line l4, any, portion of the olefin charge may be introduced into the-hydrocarbon layer in the up- Per p'ortion of the settler ID. The olefins introduced through the line l4 commingle with the hydrocarbons in the settler and are diluted thereby to produce a mixture containing a high proportion of isoparafiin to olefins, which is favorable for obtaining the alkylation reaction. Ordinarily the proportions of olefin introduced through the line [5 and the isoparaffin introduced through the line I, are such as to give an overall ratio of isoparaflln to olefin of at least 1:1 and preferably from about 3:1 to 5:1. The olefin charge is ordinarily split between a number of stages, and one skilled in the art will be able to split the olefin charge to introduce the desired amount into each stage. Ordinarily the proportions introduced in the various stages are about equal and in case the olefin charge is split between three stages, approximately one-third should be introduced through the line l4 into the settler l0.

The hydrocarbon mixture is transferred from the upper portion of the settler through the line l9 to a mixer 28, provided with a stirring mechanism 2|. In the mixer 28, the mixture of isoparafiin and ,olefins is intimately contacted with partially spent acid introduced into the lower portion of the mixer through the line 22. The reaction products are withdrawn from the mixer 28 through the line 24 and introduced inma settler 25. In this settler the acid and hydrocarbons stratify and the lower acid layer is conducted from the settler through the valve controlled line 8 to the mixer 3, referred to heretofore. Into the upper hydrocarbon layer of the settler 25 is introduced additional olefinthrough the line 26 which communicates with the olefin charging line 15. By suitable regulation of the valve 28 in the line 26, any proportion of the olefin charge may be commingled with the hydrocarbon layer in the settler 25.

The hydrocarbon mixture is transferred from the settler 25 through the line 29 to a mixer 30 provided with a stirring mechanism 3|. In the mixer 38, the hydrocarbons are contacted with sulfuric acid catalyst, comprising partially spent sulfuric acid introduced through the line 33. The reaction mixture is conducted from the mixer 30 through the line 34 to a settler 35 wherein the separation of acid and hydrocarbon is allowed to take place. The acid layer collecting in the bottom is allowed to flow through the valve controlled line 22 to the mixer 20, referred to heretofore. Additional olefin is injected into the hydrocarbon layer of settler 35, by-means of the line 31 which communicates with the olefin charging line l5, whereby a portion of ole fin may be introduced into settler 35 by regulation of the valve 38 in the line 37.

The hydrocarbon mixture is transferred from the settler 35 through the line 39 to a mixer 49 provided with a stirrer M which intimately mixes the hydrocarbon with the partially spent acid introduced into the mixer through the line 42. The reaction mixture from the mixer 48 is 7 passed through the line 44 to a settler 45 where'- in the acid separates as a lower layer from the hydrocarbons and is withdrawn through the valve controlled line 33 to the mixer 30, referred to heretofore; The hydrocarbon layer collected in the upper portion of the settler 45 is transferred through the line 41 to a mixer 48, provided with stirrer 49. While there is shown no injection of olefin into the hydrocarbon layer in the settler 45, it is to be understood that such injection may be used if desired. The final mixer 48 provides an opportunity for effecting rewith the isoparaflln.

The acid introduced into the mixer 48 is fresh or new acid, which should be about 93 to or more concentration, or preferably about 94 to 98%. This acid, which may be new or restored acid, is introduced through the line 58 by pump 5|. The amount of acid introduced is sufiicient to make the overall ratio of acid to olefin charge about 1:1 or less and preferably about .5 to .8:1. The reaction mixture is transferred from the mixer 48 through the line 53 to a settler 54. The acid and hydrocarbon separate in the settler 54 and the acid collecting in the lower layer of the settler is conducted through the valve controlled line 42 to the mixer 48., referred to heretofore. The hydrocarbons are passed from the upper portion of the settler 54 through the line 56 to a mixer 58 provided with a stirrer 59.

In the mixer 58 the hydrocarbons are intimately contacted with a neutralizing reagent, such as an aqueous alkaline solution, for example dilute caustic solution, introduced through the line 60 by the pump 6|. The mixture of neutralizing reagent and hydrocarbon is passed through the line 63 to a settler 64 wherein the neutralizing reagent settles out and may be withdrawn from the lower portion of the settler through the valve controlled line 65 or any portion thereof recycled to the mixer 58 through the branch line 66, which communicates with the line 60. The neutralized hydrocarbons are transferred from the settler 64 through the valve controlled line 61 to fractionator 68. The fractionator 68 is provided with suitable heating means, such as heating coil 69, whereby sub-. stantially all hydrocarbons within the motor fuel boiling range and lower are vaporized and removed overhead through the vapor line 10. The bottoms of higher boiling point than the desired motor fuel may be withdrawn from the lower portion of the fractionator through the line I2.

The overhead vapor removed through the va-.- por line ID are introduced into the'secondary fractionator or stabilizer 15, wherein a. separation is made between the desired motor fuel and lighter hydrocarbons, such as the normally gaseous hydrocarbons. The motor fuel fraction is withdrawn from the lower portion of the fractionator 15 through the valve controlled lin'e'16. This motor fuel may be a stable or unstable product falling within the boiling range of gasoline or a normally liquid hydrocarbon fraction of high antiknock value, suitable for blending with gasoline.

The operation in the fractionator 15 may vary considerably, but it is intended to make a separation of a fraction relatively rich in isobutane for recycling to the system. If a portion or all of the normal butane is retained in the gasoline which is drawn from the lower portion of the fractionator, the remaining products may be fractionated to obtain an isobutane cut which may be withdrawn as a side stream through the valve controlled line 18, and the lighter hydrocarbons released from the upper portion of the fractionator throughthe valve controlled line 88. The nature of the products discharged through the line 88 will, of course, depend somewhat on the character of the charging stock. For example, if the charging stock is a cracked fraction containing C4 hydrocarbons and lighter, the

cribed is ordinarily in the liquid phase.

gases discharged through the line 88 may com prise Ca hydrocarbons and lighter. If the charging stock is essentially C4 hydrocarbons, then the overhead product from thefractionator 15 may comprise essentially isobutane, which may be taken overhead through the'line 8| instead of the line 18. I

In case a portion or all of the normal butane .is separated from the gasoline fraction withdrawn from the lower portion of the fractionator 15 through the line 18, then it may be desirable to separate a C4 fraction from-the fractionator I5 and subject this fraction to further fractionation in another fractionator, not'shown, to separate the isobutane from the normal butane. In either case, the isobutane from the line I8 or 8| is passed through a condenser coil 82 wherein it is condensed andthe condensate passed through the run-down line 83 to receiver 85. Any portion of the isobutane collecting in the receiver 85 may be passed through the line 6 containing a complete reaction of the olefins in the alkyiation 35 of the isoparafllns. Ordinarily the time would be about 30 to 90 minutes, and preferably 40 to 60 minutes.

A an example of the operation of the invention, the following data were obtained on a fivestage counterflow apparatus, using as the isoparaflin charging stock a fraction containing about 98% isobutane, and as the olefin charging stock plant gas which was a topped stabilizer reflux containingabout 45% C4 olefins, and about 24% isobutane. The isobutane was contacted with the used acid in the first-stage and the plant gas was split and injected into the second and third stages.

Charge to stage No. 1 Is'obutane Charge to stage No. 2--.. Plant gas Charge to stage No. 3 Plant gas Concentration of sulfuric acid-percent 98 Acid/olefin ratio 1.18 Isobutane/olefin ratio 3.75 Temperature F 60.8 Contact time-minutes L..... 90 Percent sulfuric acid in recovered acid 94:4 311' F. fraction:

Percent yield by weight basis of olefin 146.2 Octane number CfRM. 91.6 Bromine number -1 311-400 F. fraction: j

Percent yield by' weight basis of olefin 19.1 Bromine number.. 1

It will be observedfrom the above results that using an isobutane stripping stage in which the spenteacidprionto withdrawal from the system was contacted with the isobutane charge only, the yield of 311 end point product was approximately 146%. Also, the recovered acid was of good quality and had a concentration of 94.4%.

The treatment of the used acid with isoparaffin may be used advantageously in connection with any suitable system, including countercurrent or concurrent operation, in which the acid is recycled. In such a case the recycle acid andisoparaffin may be contacted in a separate reactor, for example the initial reactor, and the olefin charged to one or more successive reactors.

The present invention'has the advantage of producing increased yields of the desired prod- 5 ucts and increased acid concentration which permits the use of a smaller fresh acid dosage and longer use of the acid. I

The feature of subjecting a solution of olefin in sulfuric acid to contact with a substantially olefin-freelow-boiling isoparaffin to strip absorbed olefin product from the acid, and then passing the resulting mixture of isoparaifin and stripped olefin product to an alkylation reaction zone where the olefin productpis alkylated by the isoparaifin in the presence of an alkylation catalyst is disclosed and claimed in copending application, Serial No. 392,874, filed May 10, 1941.

'. The feature of prediluting the olefin feed to an alkylationreaction zone with separated hydrocarbon phase or alkylate containing a high proportion of'isoparaflln prior to contacting the olefin with the alkylation catalyst is disclosed and claimed in copending application, Serial No. 392,396, filed May], 1941.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may

be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended I claims. a

We claim:

1. A process for the alkylation of isoparaflin with olefins, which comprises treating olefins and an excess of low boiling isoparafiins with strong sulfuric acid, whereby the isoparaflins are alkylated by the olefins, separating the used acid from the reaction products, separately contacting at least a portion of the used acid with substantially olefin-free isoparafiins to strip the acid of absorbed olefins, and passing the mixture of isoparafiins and hydrocarbons stripped from the acid to the alkylation operation.

2. A process for the alkylationof isoparafllns with olefins, which comprises passing strong sulflow ofthe acid and isoparaflins is concurrent.

4. A process according to claim 2 in which the flow of the acid andisoparafllns is counter-current.

AR'I'HUR R. GOLDSBY. ERNEST F. PEVERE. LOUIS a. CLARKE. GEORGE B. rm'rcn. 

